Cellular telephone systems have gained widespread acceptance as an efficient means of mobile voice and data communications. While early mobile units were large and complex, miniaturization has made possible hand-held units with full functional capabilities allowing the user freedom to use the phone unit without connection to the vehicle. Unfortunately, this miniaturization has made hand-held units less practical for vehicular use. For example, battery charging, remote antenna connections, voice and data communications, and most importantly, what is known as "hands free" operation require a physical connection between the phone unit and parts or devices found in the vehicle.
To solve this problem cellular phone manufacturers have made available car kits to provide the required features. These kits include physical hardware to retain the phone in the vehicle including an attachment for establishing an electrical connection to the phone and various types of remote speakers, microphones and antenna connections. These kits also include complex electronics modules to provide battery charging, audio amplification and digital communication interface to the phone unit.
There are a large number of models of cellular telephones in existence and each physical interconnection and electrical interface is unique to a manufacturers specific model. There are many examples of presently used physical interconnections. As a result, car kits do not provide any form of universal connection and are neither physically nor electrically interchangeable. Further, because of the large variety and relatively low volume production of these kits, users are forced to pay prices comparable to the much more complex phone unit itself to obtain these kits.
This situation has caused a hardship on cellular telephone users and affected the marketplace for new equipment. Fleet users, for example, cannot provide a universal car kit connection for the variety of phones they may acquire. Users are forced to abandon their investment in the car kit when purchasing new models of telephones. These limitations have prevented businesses such as car rental agencies from providing users with means to use their car phones in rented vehicles. Further, the high cost of these car kits has caused many users to operate hand-held units while driving, an unsafe condition which is subject to increasing governmental concern and regulation.